The contents of Japanese Patent Application No. 11-372878, with a filing date of Dec. 28, 1999, in Japan, is incorporated by reference herein, in its entirety.
The present invention relates generally to an improvement of a support structure for a valve shaft of a butterfly valve, which is used as, for example, a swirl control valve assembly for a multi-cylinder internal combustion engine.
It is well known that a swirl control valve is disposed on an intake air passage in order to variably control the intensity of swirl gas motion generated in a combustion chamber of an internal combustion engine. The swirl control valve is generally disposed in an intake manifold. The intake manifold rotatably supports a valve shaft of the swirl control valve, and valve bodies, made in a planar shape, are attached to the valve shaft. The swirl control valve opens or closes the intake air passages, each of which is connected to each cylinder of the internal combustion engine, all together by rotating the valve shaft.
Two types of swirl control valve are known; both of them are usually applied to an internal combustion engine that has a pair of intake valves on each cylinder. One type of swirl control valve has valve bodies that are partially cut off in order to make the intake air flow leaned to one side in each intake air passage. Another type has valve bodies that are disposed on the intake air passages each connected to one of the intake valves disposed on each cylinder, and the swirl control valve of this type opens or closes only one of the intake passages connected to each cylinder.
Japanese Provisional Patent (Kokai) Publications Nos. 6-117260 (1994) and 8-200116 (1996) disclose not only the swirl control valves as described above but also actuators to drive valve shafts of the swirl control valves. It is understood that these actuators are generally disposed at the end of the valve shafts.
Japanese Provisional Patent (Kokai) Publication No. 8-200116 (1996) also discloses a valve-opening sensor to detect the opening degree of the valve bodies, which is disposed at the same end of the valve shaft where the rotational actuator is connected so that the valve shaft, the actuator, and the position sensor are arranged in a line.
In the conventional structures as described above, because the other end of the valve shaft, where the actuator is not connected, is merely supported rotatably to the intake manifold, the intake manifold does not restrict the movement of the valve shaft around and perpendicular to its rotation axis. Therefore, the end of the valve shaft may vibrate within a bearing hole of the intake manifold because of the vibrations of the internal combustion engine itself and/or the change of the intake air pressure, and such vibrations of the valve shaft may cause a rattling noise.
On the other hand, if an actuator that has no return spring to continuously force the valve shaft in one rotational direction is connected to the valve shaft (for example, if an actuator driven by a step motor is connected to the valve shaft), a return spring has to be disposed in addition to the actuator because there is some amount of play at each connection between the actuator and the valve shaft. Such additional return spring may increase the complexity of the structure to some degree.
Therefore, a general object of the invention is to provide an improved support structure of a valve shaft for a butterfly valve that alleviates one or more of the shortcomings discussed earlier herein.
An object of the invention is to provide a support structure of a valve shaft for a butterfly valve that can prevent the rattling noise due to the vibrations of the valve shaft.
Another object of the invention is to provide a simple support structure of a valve shaft even if an actuator has no return spring therein.
The above and other objects of the present invention can be accomplished by a butterfly valve assembly that includes a valve shaft supported by a bearing so as to rotate around its longitudinal axis and having a first end and a second end, an actuator connected to the first end of the valve shaft, and a valve-opening sensor connected to the second end of the valve shaft and having a return spring therein, so that the valve shaft is restricted in its movement within the bearing.
Any type of valve-opening sensors may be employed, such as a sensor having a variable resistor, or a non-contact sensor that has no brush for sliding on the resister. However, regardless of the type, the valve-opening sensor generally has a return spring to prevent movable components therein from moving freely within their play. In the present invention, there is provided the valve-opening sensor having the return spring therein at the second end of the valve shaft opposite to the first end where the actuator is connected, thus the return spring can continuously apply its resilient force to the valve shaft so that the valve shaft is restricted in its movement within the bearing. For example, the resilient force is applied to both ends of the valve shaft in one direction perpendicular to the longitudinal axis of the valve shaft.
The butterfly valve assembly of the present invention may be employed as a swirl control valve that controls intake air flow in intake air passages each of them being connected to each cylinder of a multi-cylinder internal combustion engine. In this case, valve bodies are attached to the valve shaft and each of them is disposed on each intake air passage.
The butterfly valve assembly of the present invention may further include a first linkage device to connect the first end of the valve shaft and the actuator. Each component of the first linkage device can also be restricted in its free movement despite of its play. More specifically, the first linkage device may have a first arm that is fixed to the first end of the valve shaft and rotates together therewith. It has an extended end that extends in the direction perpendicular to the longitudinal axis of the valve shaft, and the actuator is connected thereto. The first arm can not only transmit the rotational force applied to the valve shaft from the return spring to the actuator but also transmit the reaction force applied to the extended end to the first end of the valve shaft as a force perpendicular to the longitudinal axis of the valve shaft, so that the first linkage device can cause firm restriction to the free movement of the valve shaft within the bearing more effectively.
Also at the second end of the valve shaft, a second linkage device can be provided to connect the second end of the valve shaft and the valve-opening sensor. Each component of the second linkage device can also be restricted in its free movement despite of its play. More specifically, the second linkage device may have a second arm that is fixed to the second end of the valve shaft and rotates together therewith. The second arm has an extended end that extends perpendicular to the longitudinal axis of the valve shaft, and the valve-opening sensor is connected thereto. The second arm can transmit the resilient force generated from the return spring to the second end of the valve shaft as a rotational force that is transmitted to the first end of the valve shaft and a force perpendicular to the longitudinal axis of the valve shaft, so that the second linkage device can cause firm restriction to the free movement of the valve shaft within the bearing more effectively.
The valve-opening sensor can be a structure such that it includes a sensor shaft that rotates around its longitudinal axis, and where the return spring applies a resilient force to the sensor shaft in one rotational direction.
Any type of actuator can be employed such as an actuator that is electrically controlled. An example of the electrically controlled actuator of the present invention generates a linear force that is made from a rotational force generated by a step motor disposed within the actuator, so that the actuator has no return spring therein.
According to one aspect of the present invention, the return spring disposed in the valve-opening sensor continuously applies its resilient force to both ends of the valve shaft in one direction, so that the valve shaft can be restricted in its free movement within the bearing, therefore the rattling noise, due to the vibration of the valve shaft within the bearing, can be prevented. Also the whole structure of the butterfly valve assembly can be simplified because the return spring prevents each connection between the valve shaft and the actuator, and between the valve shaft and the valve-opening sensor, from freely moving within its play without using additional return spring.
Also in the case when the first and/or second linkage device being provided, these linkage devices can be prevented from rattling.
Furthermore, even if the actuator has no return spring therein, there is no need to dispose additional return spring other than the one disposed within the valve-opening sensor.
Further objects, features and advantages of the present invention will become apparent from the Detailed Description of Preferred Embodiments which follows when read in light of the accompanying figures and the claims.